1. Field of the Invention
The present invention relates to an ion source and an ion implanting apparatus, and more particularly to an ion source with a discharge chamber into which microwave is introduced to induce plasma, and an ion implanting apparatus using the ion source.
2. Description of the Related Art
A microwave ion source is usually composed of a wave guide with the rectangular cross-section for transmitting microwave and a discharge chamber coupled thereto with the circular cross-section. Microwave of the specific frequency (2.45 GHz, for example) is at first generated and then introduced into the discharge chamber through the wave guide to thereby induce plasma therein. An ion beam is taken out from the plasma and irradiated to a sample. Such ion source is applied to an apparatus that changes the surface quality of the sample, processes the sample or implants impurities in the sample.
A conventional ion source of this kind is shown in FIG. 5. As shown in the figure, the ion source has microwave oscillator 1, isolator 2 located after the oscillator 1 for absorbing reflected wave to prevent the oscillator 1 from failing due to the reflected wave, power monitor 3 for measuring the amount of the reflected wave, and three-stub tuner 4 having three rods in a wave guide for providing the impedance matching (load matching) between the plasma and the wave guide of the rectangular cross-section, whereby the microwave is directly supplied from the wave guide 5b with the rectangular cross-section to the discharge chamber 6 with the circular cross-section.
In the ion source like this, the impedance between the plasma and the wave guide 5b with the rectangular cross-section had to be matched by adjusting the length of rods of the three-stub tuner 4, while monitoring reflected power by the power monitor 3.
When the maximum current is required in the conventional ion source as described above, ion beam 9 had to be extracted, while adjusting the operational conditions of the ion source, such as a flow rate of sample gas, intensity of the magnetic field applied to the source and the power of microwave. Every time when the operational conditions are changed, the three-stub tuner 4 had to be adjusted so as to minimize the reflected wave, while watching the power monitor 3. Therefore, the very complicated and troublesome manipulation was required, and hence the ion source was difficult to be dealt with.
As a result, there was a problem that it takes time as long as from three days to a week to start up the ion source. Further, there was another problem that an ion source, as well as an ion implanting apparatus using it, becomes large in size, since it must be installed with various kinds of auxiliary devices or equipment. There was still another problem that the adjustment of the source or the apparatus was very dangerous since the voltage as high as 50 kV is applied to the ion source.